Process for the manufacture of a permeable diaphragm for an electrolysis cell

Abstract

The invention relates to a process for the maufacture of a permeable diaphragm for electrolysis cells. The process consists of forming a sheet comprising inorganic fibres and a polyelectrolyte in the form of a finely divided solid which is insoluble in aqueous solutions of alkali metal halides, and of then heating the said sheet to melt the polyelectrolyte. The diaphragms thus obtained are particularly suitable for cells for the electrolysis of sodium chloride brines.

I claim: 
     
       1. Process of manufacturing a liquid permeable diaphragm for a cell for the electrolysis of aqueous solutions of alkali metal halides, which comprises forming a sheet comprising inorganic fibres and a polymer in the form of finely divided solid dispersed in said sheet, said polymer being selected from amongst the polyelectrolytes which are insoluble in aqueous solutions of alkali metal halides, and heating said sheet to at least partially melt said polymer sufficiently for said polymer to coat said inorganic fibres partially and to weld them to one another. 
     
     
       2. Process according to claim 1, in which said polyelectrolyte is selected from amongst the polyacids having from 1 to 20 acid groups per 100 carbon atoms. 
     
     
       3. Process according to claim 1, in which said polyelectrolyte comprises a carboxylic polyacid containing monomer units derived from unsaturated carboxylic acids containing up to 10 carbon atoms in their molecule. 
     
     
       4. Process according to claim 3, in which said carboxylic polyacid contains units derived from maleic acid. 
     
     
       5. Process according to claim 3, in which said carboxylic polyacid contains at least 50% by weight of monomer units derived from unsubstituted alpha-olefines containing from 2 to 6 carbon atoms in their molecule. 
     
     
       6. Process according to claim 5, in which said carboxylic polyacid is a graft copolymer of ethylene or of propylene. 
     
     
       7. Process according to claim 1, in which said sheet contains from 1% to 20% by weight of said polyelectrolyte. 
     
     
       8. Process according to claim 1, in which said polyelectrolyte is employed in the form of fibrids. 
     
     
       9. Process according to claim 1, in which said inorganic fibres are asbestos fibres. 
     
     
       10. Process according to claim 9, in which said asbestos fibres are of amphibole asbestos. 
     
     
       11. Process according to claim 1, in which said sheet is formed by dispersing said inorganic fibres and said polyelectrolyte in particulate form in an aqueous medium, filtering the resulting aqueous suspension through a perforate support to form a sheet of said inorganic fibres and polyelectrolyte, and thereafter drying said sheet. 
     
     
       12. Process according to claim 11, in which said polyelectrolyte is in the form of fibrids.